Yamaha YZ250 2021 User Manual

ENGINE
8-8
EAM30603
CHANGE OF THE HEAT RANGE OF SPARK
PLUGS
Judging from the discoloration of spark plugs, if
they are found improper, it can be corrected by
the following two methods; changing carburetor
settings and changing the heat range of spark
plug.
• In principle, it is advisable to first use spark
plugs of standard heat range, and judging from
the discoloration of spark plugs, adjust carbu-
retor settings.
• If the calibration No. of the main jet must be
changed by ±30, it is advisable to change the
heat range of spark plugs and newly select the
proper main jet.
TIP
• When checking the discoloration of spark
plugs, be sure to stop the engine immediately
after a run and check.
• Avoid racing.
• When changing the heat range of spark plugs,
never attempt to change it more than ±1 rank.
• When using a spark plug other than standard,
check its heat range against the standard and
check that it is a resistance type.
• Note that even if the discoloration seems prop-
er, it may slightly vary with the spark plug mak-
er and oil in use.
Standard spark plug
BR8EG
(resistance type)

Yamaha YZ250 2021 Specifications

General

Engine Type	249cc liquid-cooled 2-stroke; reed-valve inducted
Bore x Stroke	66.4mm x 72.0mm
Compression Ratio	8.9~10.6:1
Ignition	CDI
Transmission	5-speed; multiplate wet clutch
Final Drive	Chain
Suspension Rear	KYB® single shock; fully adjustable, 12.4-in travel
Brakes Front	Hydraulic disc, 270mm
Tires Front	80/100-21
Tires Rear	110/90-19
Width	32.5 in
Height	50.8 in
Wheelbase	58.5 in
Ground Clearance	14.2 in
Fuel Capacity	2.1 gal
Wet Weight	227 lb
Fuel Delivery	Keihin PWK38S carburetor
Suspension Front	KYB® Speed-Sensitive System inverted fork; fully adjustable, 11.8-in travel
Brakes Rear	Hydraulic disc, 245mm